Lubricating grease manufacture and apparatus therefor



Oct. 19, 1943.

LUBRICATING GREASE MANUFACTURE AND APPARATUS THEREFOR Filed Aug. 19, 1941 CONDLNSR .DR UM PUMP WTR .zmmv a O n fb-(5:2 o rA 6 7/ L l l 8 24 H L Q 0 ,RETURN LINE L ,Il /0/ Flu/lio 50A grvlcx /2 c ocLEz ,versn/Nc /6 /7 "Zigi/4L son? PUMP f G O Q O erstma EA TER au. pvp/P s /9 FlLTn 2 2 rrr 2 rnv/sue D 2 a' 12a/u a /v/xszz TA NK FIG-I Patented Oct. 19, 1943 UNITED STATES LUBRICATING GREASE MANUFACTURE AND APPARATUS THEREFOR Austin E. Calkins, Westfield, N. J., assigner to Standard Oil Development Company, a corporation of Delaware Application August 19, 1941, Serial No. 407,406

15 claims.

This invention relates to a novel process for manufacturing lubricating greases and for apparatus to be used for such processes; more particularly it relates to an improved process which is more convenient and economical than those of the prior art, and especially adapted for the manufacture of lime soap greases.

Heretofore mineral lubricating greases have usually been made in large kettles, either steam heated or directly fired and adapted for open cooking, or cooking under pressure a mixture of saponifiable material, such as animal fat, and a saponifying agent, with or Without small additions of water and/or mineral oil. Such cookers having suflicient capacity to handle all the grease required to be manufactured are very expensive and require a large amount of space.

One object of the present invention is to provide a grease manufacturing equipment which avoids the use of large cooking kettles; another object is to accomplish a grease manufacture in equipment which requires much less plant iloor space than processes used heretofore; and another object is toprovide a process and apparatus which can be operated economically and eiliciently and which can be readily adapted to produce the various types and grades of lubricating greases required for the market. Another object is to provide an apparatus which involves far simpler and smaller moving parts than a pressure kettle.

Broadly, the invention comprises making a lubricating grease soap stock by mixing a saponiiable material and a saponifying agent (with or without small additions of other materials, such as water, mineral oil, etc.) in a large, unheated mixing zone, heating small portions of the resultant mixture outside of the'mixing zone, and recycling the same to the mixing zone until the entire mixture has been substantially completely saponied by use of a plurality of mixing zones, one or more of which can be used for mixing while the soap stock from another is being discharged either into storage or into suitable greaseblending equipment. The invention is particularly adapted for preparing a continuous supply of soap stock which in turn is intended to be continuously and directly fed into a continuous grease-blending unit continuously compounding controlled proportions of the soap stock and mineral oil, which continuous blending is claimed in copending application 342,081 iiled June 24, 1940, of which the present application is a continuation-in-part, thus providing a simple and efficient process and apparatus for the continuous manufacture of lubricating greases which have heretofore been made by batch processes.

The invention will be better understood from a description of the accompanying drawing in which Fig. I illustrates in a schematic layout one embodiment of the invention, and Fig. II shows an alternative method of charging a mixing zone, although it is not intended that the invention be limited to the particular type of equipment used, where other equipment, somewhat different in shape, for instance, would accomplish the same or substantially equivalent purposes.

As indicated in the drawing, one or more mixing tanks I (two are shown in Fig. I) are provided for mixing the materials to be used in making a concentrated soap stock. These materials may either be fed in at the top by opening or removing the lid, or, as shown in Fig. II, may

'15 be fed in through suitable inlet feed lines, i. e.,

the fat or other saponiiiable material through line 2, represented as a screw conveyor feed, the lime and water being suitably fed in as a slurry through line 3, and the mineral oil, if desired, through line 4, or these various materials may be l measured in separate vessels and Pumped in through line 23 as will be explained later. The mixer I is provided with an outlet suitably located, such as part-way up one side, for pumping the 25 saponification mixture through line 5 by means of pump 6 into heater l, which may be of any convenient type, but preferably consists of a steam-heated pipe coil. In this heater, the portion of saponication mixture being fed through it is raised to a temperature at least as high as saponiiication temperature, e. g., between the approximate limits of 250-550 F.. or for a lime soap stock, preferably between the approximate limits of 300 F. and 400 F., and the saponiiication mixture, which is at least partially saponifled by the thus described heating, is recycled by line 8 back to the bottom of the mixer I.

An important feature of the invention is that the pump 6 which may suitably be a high capacity lgear pump should have a high capacity relative to the volume of the mixer I and should be able, for instance, to circulate a volume of ma-` terial equal to the volume of the mixer in less than 2 or 3 minutes. The heating and recycling is continued until the entire mixture of materials is substantially completely saponied, at which time the valves at the bottom of the mixing tank I are reversed, i. e., by closing the valve on the recycling line 8 and opening the discharge valve in line Ill, from which the saponied mixture is now withdrawn as a finished soap stock which may be either passed toetorage with or Without 'going through the cooler II, or if desired, passed on through line I2 to a suitable grease-mixing equipment. This latter may be designed for batch operation in conventional kettles or, preferably, continuous as shown in the drawing, namely, by passing the soap stock from line I2 through a metering soap pump I3 to 60 a high-speed mechanical mixer Il, such as a Lancaster disperserLinto which mineral oii of suitable viscosity from a suitable source (not shown) is fed through line I l, oil heater il, line I'l, and metering oil pump l 0. I'he finished lubricating grease is discharged from the mixer I4 through line i and, if desired, through a filter and a pressurecontrol valve 2i and finally through outlet 22. By-pass line 24 is used if it is desired to feed raw material into mixers i by means of line 2J.

Connections should be made to the mixing tanks, circulating pumps, heater, and various lines through which fat or soap stock must pass, so that they may be blown clear of soap ingredients before being allowed to cool. A plurality of mixing tanks may be so connected that while one is being discharged through the cooler into the grease-mixing equipment, one or more other mixing tanks are being used for mixing and heating other batches of soap stock, with the result that a substantially continuous supply of soap stock is maintained for feeding to the greasemixing equipment. If more than two mixing tanks are to be used for mixing at the same time, one or more additional heaters and circulating pumps may be used.

If desired, an auxiliary heater or cooker may be provided in line |00 in order to give the soap stock being discharged fromthe mixing tank a final heating before going to the grease-mixing equipment, with or without the use of the cooler il.

Instead of using steam for heating the heater 1, one may use higher boiling heating media, such as dlphenyl oxide (boiling point 288 C.) which, when vaporized like steam, permits the use of temperatures up to 750 F. or so, as for use with sodium soap which requires about 450 F. for good fluidity, or mixed heating media, such as mixtures of diphenyl oxide and diphenyl, mercury, etc., or high temperature liquid heating media, such as molten salts, or hot gases, such as ilue gas or other combustion gases, or direct firing may be used, if desired, although steam is preferred for temperatures below 350y F. because it is cheapest and adapted to emcient and accurate control of the temperature and leads to the production of uniform quality in the soap stock.

If desired, an auxiliary pump may be used to assist in discharging the soap stock from the mixing tanks through line i0, or these tanks may be discharged by building up a pressure in the top of the tank by steam or other fluid pressure.

A condenser 25 may be provided in order to condense steam which may be drawn off from the top of the mixing tank i and also, if desired, to recover glycerine vapors.

Suitable shut-off valves, thermometers, thermostats, -safety valves, and pressure control valves are provided in order to carry out the invention as described; preferably, the equipment is designed for continuous, automatic operation for the manufacture of the soap stock, and this, in turn, is combined preferably with a continuous and automatic grease-blending operation.

The cooler I i may be of any suitable construction, such as a straight section of pipe, or one or more coils of pipe passing through a wateror oil-cooling jacket or shell, or preferably of the scraped screw type.

If an auxiliary heater is used in line I0, the rate of feed therethrough should be regulated with the time (according to the length of internal pipe) so that there will be a constant flow of soap stock to the grease mixer, if desired.

As an example of the use of the above-described equipment, it may be mentioned that if a calcium soap stock is to be made from a mixture of hog fat and hydrated lime, based on 20% fatty acid, a temperature of about 250 F. is required to insure a iiuid condition at all times in4 order to obtain a substantially homogeneous mix/- ture, and in order to insure complete saponiilcation, the temperature is preferably raised somewhat higher, e. g., between about 300 and 400 F., this being accomplished either entirely in the heater 1, or partly therein and partly in a slurry heater (not shown) in line i0, as suggested above. heated in a heater (not shown) ahead of line 2.

Operation of a soap-manufacturing unit, such as described above, has demonstrated that the time required to prepare one mixer volume of satisfactory grease soap stock is less than l hour, compared to at least 31/2 or 4 hours heretofore required with the customary pressure-kettle operation. Large savings in equipment cost are also realized. Operation of a unit according to this invention indicates, for instance, that a manufacturing plant no larger than 6 x 6 x 13 feet using three mixing tanks consisting of round pipes 6 feet high, 20 inches in diameter, and truncated at the bottom, has sufficient capacity for producing about 6,000,000 to 8,000,000 pounds of lubricating grease per year.

As indicated in the drawing, the mixing tank i preferably consists of a vertical pipe with a truncated bottom, because this type of mixer obtains suitable mixing of the ingredients by the mere pumping oil' through an outlet part-` way up the side and recycling the heated materials back into the mixer at the bottom; if desired, baille plates may be used to assist in obtaining desired mixing. Also, if desired, mechanical mixing, as with a motor-driven stirring arm or blade, may be used, although normally this is not necessary. Various other types of mixing zones may be used as, for instance, an almost horizontal, rotary drum adapted to be fed in slowly at the higher end and to be slowly and 4continuously discharged at the lower end. Such a drum may be provided with baille plates to assist in mixing the ingredients or with a stationary or rotary mechanical mixing arm. The large capacity screw conveyor can also be used as the mixing zone, the materials being fed in at one end and discharged continuously at the other'end, although in this case provision would have to be made to reverse the direction of the screw conveyor after the recycling is finished in order to draw off the soap stock into the greaseblending equipment, or else provide an outlet between the screw conveyor and the heater for drawing off the finished soap stock.

The saponiflable material to be used may be any of the fats, fatty oils, fatty acids, etc., commonly used for making lubricating grease. Specific examples of such materials include beef stearin, mutton tallow, hog fat, oleic acid, stearic acid, tallow fatty acids, lard oil, soya bean oil, cottonseed oil, corn oil, heats-foot oiland similar animal and vegetable oils, hydrogenated fatty oils, such as hydrogenated fish oils, or synthetic fats and acids, such as wax oxidation acids, etc. Of these various types of materials, hog fat, degras, lard oil, tallow, oleic acid, and other fatty acids are preferred, especially for making lime soap greases.

As the saponifying agent, lime is preferred and this may be used either in the form of calcium If desired, the fat may be pre-- caustic soda, caustic potash, lithium hydroxide, l

gelatinous aluminum hydroxide, etc. If desired,

alkali metal soaps may be converted into corresponding aluminum soaps, as by treating with aluminum sulfates. Also, mixtures of several diii'erent saponifying agents may be used,such as, lime and soda, lime and potash, soda and barium, lime and barium, etc.; in such mixtures the saponifying agent from group Ii-A of the Mend'eleefi Periodic Table should preferably be at least 90% of the total base.

As indicated earlier, it is desirable with certain types of greases, particularly the lime greases, to have a small amount; of water present in order to obtain the best grease structure and the optimum yield, expressed in volume of grease produced for any particular soap content. For lime soap greases, it is preferable to have a water content of approximately .05 to .15% of water for each percent of lime soap present. For other given for soapstocks made from three diiferent than lime soap greases considerably less water should be present, for instance, in a soda soap grease the maximum water content should be about 1%, i. e., soda soap greases are usually substantially dehydrated; and in the case of aluminum soap greases generally the water content should be or as near thereto as is practicable. If the saponiiiable material used is a glyceride or a mixture of glycerides, some glycerine is formed as a by-product of the saponication reaction, and whatever water is desired in the finished grease must be added, and, in fact, generally a slight excess of water must be added initially, in order to compensate for the small amount of water which is lost by Vaporization during the preparation of the soap stock and final grease blending. On the other hand, if fatty acids are used as the saponifable material, then some water is formed as by-product during the saponcation, and in such a case little, if any, additional water need be added.

As referred to earlier, it is possible to make various soap stocks without having any mineral oil present, but it is preferred to prepare the soap stock in the presence of a small amount of mineral oil, usually less than 30% of the weight of saponiable material, and preferably about of the weight of saponiiiable material. The mineral oil for this purpose may be of any particular type, as to whether it is paraiiinic, naphthenic, or mixed base oil, although parainic is usually preferred, and of the particular boiling range and viscosity range intended to be used in the finished grease composition; or, since only a relatively small amount of the oil is used in making the concentrated soap stock, a mineral lubricating oil of widely varying boiling range and viscosity may be used for this purpose, as one example, an oil having a relatively pale color and a Saybolt viscosity between the approximate limits of 40 seconds and 60 seconds at 210 F., this concentrated soap stock then being blended with a much larger proportion of a mineral oil of the desired characteristics for making the finished lubricating grease.

As a general guide for the preparation of concentrated soap stocks according to this invention and the subsequent blending of the latter with mineral oil to form the finished lubricating greases, the following table is given to show the approximate range of proportions of materials to be used (expressed in percent by weight). Since the amounts required, or at least preferred for best operation, differ according; to the type of base or saponifying agent used, proportions are bases, namely, calcium, sodium, and aluminum.

Table Concentrated Soap Stock Finished .v A ou n.0 soap Glyc- 9 0.50 3-12 4me 0-8 1-35 35-70 o-1 ati-75 0-8 1-35 lsoo ils-5o 0-6 1-15 In the table, the portion dealing with the concentrated soap stock shows not only the proportion of soap but also the use of water and glycerine in some instances and indicates that some oil is always used, because operations (especially the final grease-blending) are substantially facilitated when some mineral oil is present in the preparation of the soap stock, although, as explained previously, it is possible to make the soap stock without any mineral oil. In the portion of the above table pertaining to the finished grease composition, only the figures are given for the soap content, because greases are usually blended from controlled amounts of soap stock and mineral oil in order to obtain a grease of some particular soap content as required by the purchasers specifications; the amounts of mineral oil, water, and glycerine in the finished grease can readily be calculated from the amounts of those constituents in the soap stock and the proportion of mineral oil blended with the soap stock.

Although the invention is particularly adapted to the preparation of concentrated soap stock to be subsequently blended with a large proportion of mineral oil to make a finished grease, it is also possible to use the same. equipment for directly producing a finished lubricating grease, by merely using the correct final amount of mineral oil in the originalmixture Ordinarily,how ever, this procedure is not preferred because the large amount of mineral oil present dilutes the saponiiication mixture, and, therefore, usually requires a somewhat higher temperature or longer time to insure complete saponication, and also because from a practical plant operation point of view, it is usually suitable and more convenient to make the various grades of lubricating grease having different penetration and viscosity characteristics by making a large batch of concentrated soap stock and blending portions thereof with Various amounts of mineral oil, rather than making up separate batches of soap stock for each grade of grease.

For the sake of illustration, the following specic examples are given:

through a heater oi.' 19.0 sq. ft. inside surface with 115 1b. persq. 1n. steam outside. In 4o minutes the temperature had risen to 321 F., and the soap concentrate was discharged to an open kettle. It was 99.5% saponiiied, which is much better than the usual 9598%g achieved in 2 hours pressure kettle cooking. 'I'he concentrate was blended with oil to give the usual production oi were charged to the tank and circulation started.

produce a soap stock having the above composition, in an unheated .mixing tank, continuously withdrawing small portions oi' the resultant saponiilcation mixture and heating same outside 'I'he heater steam was at 80 lb. per sq. in. IIn

one hour the temperature was 285 F. Steam was vented from a pressure of 45 1b. per sq. in. to atmospheric pressure in the course of another hour, leaving a substantially dehydrated mass of excellent soda soap grease base.

It is not intended that this invention bellimited to the speciilc examples recited, nor to the particular types of equipment shown in the accompanying drawing which are given merely for illustratiombut only by the appended claims in which it is intended to-claim all novelty inherent in the invention.

I claim: 1. The process of making lubricating materia which comprises mixing a saponii'iable material, a saponiiying agent and a small amount of mineral oil, heating relatively small portions oi' the resultant mixture outside of the mixing zone to a temperature at least as high as the saponiilcation temperature, and-recycling the same continuously' to said mixing zone until the entire mixture is saponiiled.

,2. Process according to claim 1 in which the mixing and recycling are effected by means of a pump having a sumciently high capacity to circulate a volume oi' material equal to the volume oi' the mixing zone in a period oi less than 3 minutes. v

3. The process of making a calcium soap stock for manufacturing lubricating greases which comprises mixing a saponiflable material, a calcium saponifying agent and a small amount of mineral oil in a mixing zone, heating small portions of the resultant mixture outside of said mixing zone in a pipe-coil heater to a temperature at least as high as saponification temperature, and continuously recycling the said mixture to the mixing zone until the entire mixture is substantially completely saponifled, said mixing, heating, and recycling being carried out in a closed system under a superatmospheric pressure.

4. A process according to claim 3 in -which animal i'at and hydrated lime are used and the saponiilcation mixture is heated to about 300400 F.

5. The process of making a calcium soap stock having approximately the following composition, in percent by weight:

Material: Per cent Calcium soap 45-70 Water 5-12 Glycerine 0- 8 Mineral oil -50 for use in preparation of lubricating greases, which comprises mixing animal fat, hydrated lime, and mineral oil in proportions required to `of the mixing tank in a steam-heated pipe coil to impart thereto a temperature of about 300400 F., and continuously recycling said heated portions to the mixing zone until the en tire mixture is substantially completely saponined, and then discharging the finished calcium soap stock from the mixing tank.

6. The process of making a-lubricating grease soap stool:y which comprises mixing a saponiiiable material, a saponifying agent, and a small amount of mineral oil in an unheated mixing zone, continuously heating small portions of the resultant mixture outside of the mixing zone in a steam-hated pipe coil to a temperature at least as hi h as saponincationtemperature, and continuously recycling said heated portions to the mixing. zone until the entire mixture is substantially completely saponiiied, and nally stopping the circulation through the heater anddischarging the finished soap stock through a cooler.

7. 'I'he continuous process of making a lubricating grease soap stock which comprises mixing a saponiilable material, a saponiiying agent, and a small amount of mineral oil alternately in a pluraiityof unheated mixers, withdrawing small portions of the resultant mixture from at least A one of said mixers, heating said small portions loutside o1' the mixer to a temperature at least as high as saponiiication temperature, and recycling said heated portions to the mixer from which they were withdrawn, repeating said withdraw ing, heating, and recycling until the mixture is substantially completely saponifled', then starting a similar mixing, heating, and recycling in at least one other mixing zone, and gradually discharging the soap stock from the rst mixing zone at such a rate that said zone will become substantially empty at about the time when the saponication of the second mixing zone is substantially complete, thus coordinating the rate oi saponication and discharging that a substantially continuous flow oi' ilnished soap stock is produced.

8. Process according to claim 7 in which the mixingheatlng, and recycling to any one mixing zone is stopped after the mixture has been heated sufilciently to effect partial saponiflcation but stopped before the saponication has been completed, and then the mixture being ilnally discharged from the mixing zone is passed through an auxiliary heater wherein the saponification is completed and the finished soap stock is discharged at the desired temperature.

9. The continuous process o1' making a lubricating grease which comprises mixing a saponiable material, a saponiiying agent, and a small amount of mineral oil alternately in a plurality of unheated mixers, withdrawing small portions of the resultant mixture from at least one of said mixers, heating said small portions outside of the mixer to a temperature at least as high as saponiflcation temperature, and recycling said heated portions to the mixer from which they were withdrawn, repeating said withdrawing, heating, and recycling until the mixture is substantially completely saponiiied, .then starting a similar mixing, heating, and recycling in at least one other mixing zone, and gradually discharging the finished soap stock from the ilrst mixing zone at such a rate that said zone will become substantially empty at about the time when the saponiiication of the second mixing zone is substantially complete, thus coordinating the rate of saponication and discharging that a substan-v tially continuous flow of finished soap stock is produced, and continuously blending the resultant soap stock in controlled proportions with heated mineral oil to produce a finished lubricating grease.

l0. The continuous process of making a calcium base lubricating grease which comprises continuously making a calcium soap stock having approximately the following composition, in percent by weight:

Material: Per cent Calcium soap 45-70 Water -12 Glycerine 0- 8 Mineral oil -50 other mixing zone, and gradually discharging the calcium soap stock from the first mixing zone at such a rate that said zone will become substantially empty at about the time when the saponiflcation of the second mixing zone is substantially complete, thus coordinating the rate of saponiiication and discharging that a substantially continuous flow of finished calcium soap stock is produced, and continuously blending the resultant calcium soap stock in controlled proportions with heated mineral oil to produce a finished lubricating grease. y

11. The process of making a lubricating grease which comprises mixing a saponifiable material and a saponifying agent in proportions to produce a lubricating grease soap stock, in an unheated mixing zone, continuously withdrawing small portions of the resultant mixture and heating said small portions outside of the mixer to a. temperature at least as high as saponication temperature, recycling said heated portions to said mixing zone, and repeating said withdrawing, heating, and recycling until the entire mixture is substantially completely saponified, discharging the nished soap stock from said mixing zone through a temperature regulator to impart to the soap stock the temperature required for greaseblending, and blending the resultant soap stock in controlled proportions with heated mineral oil to produce a finished lubricating grease.

12. The process of making a soda base grease soap stock which comprises mixing a saponiable material, caustic soda and a small amount of mineral oil, heating relatively small portions of the resultant mixture outside of the mixing zone to a temperature at least as high as the saponii-lcation temperature and recycling same continuously to said mixing zone until the entire mixture is saponied, and substantially completely dehydrating the resultant soap stock.

13. Apparatus for manufacturing lubricating grease which comprises at least one unheated mixer, means for feeding soap-making materials thereinto, a heating zone outside said mixer, means for continuously circulating small portions of material from the mixer through the heater and for recycling them into a different part of said mixer, and means for blending the resultant soap stock with mineral oil.

14. Apparatus for the continuous manufacture of a lubricating grease which comprises a plurality of mixers connected so as to be used alternately, means for feeding soap-making materials into feed mixers, a heating zone outside of said mixers, a pump for circulating small portions of material from any one of the mixers through the heater and recycling same into the mixer, means for discharging finished soap stock from said mixers to a continuous grease-blending equipment comprising a high-speed grease mixer, means for continuously feeding controlled amounts of soap stock and heated mineral oil stock into the grease mixer, and means for continuously withdrawing the resultant grease through a cooler.

15. An apparatus according to claim 14 in which the mixers consist of substantially Vertical pipes truncated at the bottom, adapted to be charged at the top, pumped out through an outlet located part-way up the side for heating, and adapted to be recycled into the mixer at the bottom.

AUSTIN E. CALKINS. 

